Patent GB-644200-A (GB)
Title: Method and apparatus for tying string in a clove hitch
IPC: B65B51/08
Filed: 1946-10-02
Abstract: 644,200. Securing packages by tying up. RECKITT & COLEMAN, Ltd., UPTON, J. B., and RYMER, D. W. Oct. 2, 1946, No. 3487/50. Divided out of 644,126. [Class 94(i)] A method of tying a clove hitch round an article comprises the step of feeding a continuous supply of string to a tying head, seizing its leading end by the tying head, forming it into two loops around the article by consecutive rotations of the head in opposite directions, seizing the trailing end by retractable gripper means external to the head, and pulling it through the second loop. The invention is described as applied to the machine for wrapping blocks of washing blue described in Specification 644,126. String 173', Fig. 9, is fed from a bobbin (not shown) on the machine frame, through a pair of plates 182 which are pivotally mounted on the frame and are operatively connected with a mercury switch 184 in the circuit of the machine driving motor. The string is guided by pins 178, 185 and a member 179 and the arrangement is such that a knot or irregularity in the string engages the plates 182 and stops the machine. The string (173") then passes through a draw-back device comprising two pairs of upright members 188 rigid with a frame bracket 187 and each carrying string retaining hooks 189 and cooperating spring-pressed balls 191 at their upper ends. A gripper 193 is pivotally mounted on an L-shaped extension 192 of the member 187 and co-operates with string-engaging grooves 194 in the uprights 188. Cross-bars 190 are aligned with the spaces between the members 188, and are connected with a cam-actuated lever 195. The arrangement is such that the gripper is inoperative in the upper position of the lever 195 but is operative during vertical reciprocation of the bars 190 which on their downward movement, draw the string through the plates 182 and draw back excess string from the tying head. The string (173<111>) passes from the draw-back device, via a guide 196, Fig. 15A, to a tying head 160 comprising an inverted cup-shaped member carried by a spindle 212, Fig. 11, rotatably journalled in the machine frame. The spindle 212 is given a predetermined degree of movement in both respective directions of rotation by means of a roller chain (not shown) passing over a sprocket 215 and connected at one end by a spring to the frame and at the other to a camactuated link. The head 160 carries a gripper 203, downwardly urged by a blade spring 203a so as to hold the string in engagement with the upper edge of an annular ledge 208. The gripper however may be retained in two other positions by a spring catch 203c when it engages respective steps 203f, 203d formed on the gripper. When the catch 203c engages the step 203f the string is completely free to leave the ledge 208. When the step 203d is engaged the string is free to move circumferentially relative to the ledge but not radially outward therefrom. The gripper 203 and catch 203c have respective extensions by which they are operated at appropriate instants in the tying cycle by a forked member (not shown) pivoted to the machine frame and actuated by cam mechanism. The forked member also operates a string cutter 222 which is detachably held in position by a blade spring and knurled nut (not shown). The guide 196 has a limited upward and downward movement by means of a camactuated link 198 and comprises a bar 197 and a blade 205, between which the string passes, and guide studs 204, 206. The pressure of the blade 205 is regulated by a spring-loaded nut 207. Co-operating with the tying head is a hook 278, Fig. 13, which is slidable with respect to a channelled support 276 under the action of a lever 279 and cam-actuated push-rod 285. Sufficient movement of the lever 279 will also move the support 276 relative to a supporting yoke 272 in which it is slidably mounted. A spring (not shown) connected between the support 276 and the yoke 272 tends to urge the support 276 into the position shown in Fig. 13. The wrapped block is held in one of four cylindrical holders 150, Fig. 5, which are carried at the outer ends of respective arms rigid with a central rotatably-mounted member. Each holder 150 is capable of vertical movement relative to its associated arm, under the action of cam mechanism (not shown). The holders 150 constitute a rotary carrier for the articles whereby they are successively moved from the wrapping station to a position under the tying head, and after tying are carried to a delivery shoot (not shown). The carrier is rotated in synchronism with the other machine movements by a Geneva mechanism (Figs. 3 and 4, not shown). The cylinder 150 has a gripper formed by string-engaging hook 245 carried by a plate 142 which is mounted for vertical sliding movement against the action of a spring 247 and is carried by an arm 253 mounted for movement about a pivot axis 253' under the action of a cam-actuated roller 257 and in opposition to a spring 255. The hook 245 may be raised vertically under the action of a cam-actuated push rod 252 rigid with a stop 251 in abutment with the lower end of plate 242. Operation. As the cylinder 150 is bringing the package concentrically below the tying head 160, Figs. 15A and 15B, the latter commences to rotate anti-clockwise and the leading end of the string which lies in the gripper 203 is carried around the neck 149 of the package, the string guide 196 being in its lower position so that the string passes under the ledge 208. After one and a quarter rotations the leading end is brought into engagement with the hook 245 on the cylinder 150, Fig. 16A, by which it is now retained. The member 276 is then extended and the cylinder 160 commences to rotate clockwise, the leading end of the string being released by the gripper 203. The string guide 197 is raised above the level of the ledge 208 and the trailing portion coming from the string guide is engaged by a hook 220 carried by the tying head adjacent the gripper 203 so that the string is drawn round on the ledge 208. The string portion extending between the hook 220 and the package neck 149 is caught on the member 276, Fig. 17A, which has been extended for this purpose. The string is retained on the ledge 208 by hooks 209 and pins 268. The hook 278 is now extended and engages the string portion between the hook 220 and the package neck as it comes round the second time and retracts to draw the trailing end of the string through the loop last formed. The cutter 222 is actuated to sever the string, and the cylinder 150 is lowered relative to its associated supporting arm to move the package clear of the tying head. The carrier then commences to rotate and so moves the cylinder 150 away from the tying head (Fig. 19A, not shown). The trailing end of the string between the hook 278 and the package neck is drawn tight by this movement, and at the same time the arm 253 is rotated relative to the cylinder 150 to tension the leading end. The catch 203c has meantime been engaged with the step 203d of the gripper 203 so that the string remaining on the ledge 208 can pass under the action of the draw back device back through the gripper without being wholly released therefrom.